The state attorney general's office said Tuesday that Arizona's supply of a drug used in lethal injections came from England, marking the first time a state has acknowledged obtaining sodium thiopental from an overseas source since a shortage of the drug started affecting executions in the U.S. this year.

A federal judge on Monday blocked the scheduled execution of an Arizona death row inmate, saying more time was needed to consider a challenge to the use of a knockout drug from an unidentified manufacturer.

A knockout drug that Arizona plans to use in an upcoming execution was not made by the sole U.S. manufacturer, which means it likely came from another country, attorneys said during and after a state Supreme Court hearing Wednesday.